I'm assuming that the mesh is for air circulation under the nest, or it's
an attempt to prevent bird blow fly issues. You can use clear caulk to
ensure that the seams of the box are waterproof, and since there are holes
in the floor and a ventilation slot, I wouldn't worry much about the mesh.
The elevated mesh might be a good solution if blow flies are numerous. We
have had bird blow fly larvae in our bluebird box, although not enough to
do noticeable harm to the nestlings. I've occasionally lifted the nest
with a metal spatula and placed diatomaceous earth under it to try to
control blow fly larvae, but I've also read that they are only a real
problem if there are more than about 10 larvae per nestling. It would be
interesting to know if anyone locally has seen blow flies in such numbers
that they weakened or killed the nestlings. Once the nestlings have
fledged, we remove the nest and place it in a freezer bag, and freeze it
for a week or so. Then the old nest and dead blow fly larvae go in the
compost, rather than hatching and starting the cycle again with the next
clutch.
On the subject of bluebird nest boxes, one thing to check is that the
entrance hole is 1-9/16" in diameter. Many boxes are designed with 1-1/2"
holes for Eastern Bluebirds, but supposedly, the largest male Western
Bluebirds (and Mountain Bluebirds) can't fit into this hole size. The hole
can be enlarged slightly with a rasp, but if it's bigger than 1-9/16",
starlings can enter the box.
Most boxes for Eastern Bluebirds have a small floor area of only 4"x4", but
many bluebird organizations recommend a floor size no smaller than 5"x5"
for Westerns. The reasons they give include the Western Bluebird's larger
average clutch size and the larger floor helps nestlings spread out during
hot weather. The nestlings also flap their wings in the box before
fledging, so they probably appreciate having enough space. Bluebirds will
take almost any box if they have to, but the larger size may have some
benefits.
Lisa Millbank
On Tue, Mar 17, 2020 at 5:07 PM Carma Sue Henry <cshenry at bywordofmind.com>
wrote:
> BUYER BEWARE - Just had a box of 4 of these (below) bluebird boxes sent to
> our house from Albany Home Depot. Although the description says they come
> with the mesh screen to raise the nestlings off the bottom of the nest,
> THEY DO NOT! Customer service checked and none of their remaining stock of
> this brand had them either - error in online listing OR in mfgr packing.
> Home Depot does not stock the risers separately, although I was able to
> source them elsewhere. The lady I spoke with graciously refunded my money
> without asking that I return them. Our tool set up is still in too much
> disarray to do any DIY projects but we ought to get the mesh risers in a
> couple of days and be ready if any more WBBs show up.WILD WINGS Cedar
> Bluebird Box House$17.98_______________________________________________
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